Gas valve

ABSTRACT

A valve ( 100 ) for controlling gas flow for a gas heating which allows, as different embodiments, (1) A gradual and smooth transition from high flow to low flow. This is achieved by a rotatable control means ( 108 ) wherein the valve body or control means has a taping groove ( 134 ) on an annular path intersecting with a port to allow variation in flow rate as the control means rotates. (2) The ganging together into modular form of several valve units with the inlet ports forming a common inlet manifold. (3) The control means, at least, is a plastic, eg nylon. (4) The switching to off from either high or low flow is allowed. But the switching from off to on is directly to high flow. The switching from off to on is prevented from going to low flow directly

FIELD OF THE INVENTION

The present invention relates to use of a valve particularly but notsolely referring to an improvement in the control over the flow rate ofgaseous fuels.

BACKGROUND TO THE INVENTION

It is well known in the art that a simple rotating ball valve may beused to control the flow of gases. However, such prior art devicescommonly suffer a lack of control in adjusting the flow rate to anythingother than a high setting. For example, consider FIG. 1, with a graphcomparing flow rate against control rotation for a typical prior artvalve. There is a very abrupt change between the low setting 11 and thehigh flow rate setting 12, which occurs over a very small angle as istherefore very hard to accurately achieve flow rates in between thesesettings. This is particularly important in applications such as a gascook top where, for example, a chef might require very fine control overthe heat applied to the cooking vessel in order to achieve a particularstyle of cuisine. This may require either remarkably dexterous controlover the gas valve or intricate mechanical arrangements in order toimprove the level of control, especially at low flow rates.

For example, Korean Patent 9208198 issued to Rinhai Co discloses asolenoid valve in order to electronically achieve improved control overthe flow rate over a wide range of flow rates, U.S. Pat. No. 5,009,393issued to Harper-Wyman Co discloses a linear turn down metering valvewith improved controllability. This device however is difficult tomanufacture and is quite complicated in construction. It would bedesirable to have a simpler construction and to use more efficientmaterials.

It is also well known in gas valves to have the valve going from thehigh flow setting to the off setting and vice versa in one movement.This is so that when the burner or heater is started the maximum flowrate of gases is supplied to assist the correct ignition of the flame.It would be dangerous to start the flame with a low flow setting as ifthe gas was not to ignite a build up of gas could occur with a resultingdanger of explosion. Accordingly conventional gas valves only allowrotation to the off position in one direction and have a stopper toprevent any rotation between the low flow setting and the off flowsetting. However it would be desirable to allow the gas valve to beswitched off from a low flow setting but to also ensure that the gasvalve could not be switched on to a low flow seeing from the offsetting.

SUMMARY OF THE INVENTION

Accordingly it is an object of the present invention to provide animproved gas valve which goes some way to overcoming the abovedisadvantages, or which will at least, provide the public with a usefulchoice.

In a first aspect the present invention consists in a valve forcontrolling a flow of fluid comprising:

a body portion including a fluid inlet and a fluid outlet through whichsaid flow of fluid pass in use, and

control means for restricting said flow of fluid between said fluidinlet and said fluid outlet located within said body portion andadjustably rotatable therein,

wherein one of said body portion or said control means includes atapering groove on an annular path and the other includes a portintersecting with said annular groove such that the position of saidintersection varies according to the angular position of said controlmeans, such tat in use there is a gradual variation in the flow rate ofsaid flow of fluid with respect to variations in the angular position ofsaid control means, over a substantial angle of rotation of said controlmeans, said intersection being within a flow path between said fluidinlet and said fluid outlet.

In a second aspect the present invention consists in a valve forcontrolling a flow of fluid comprising:

a body portion including a fluid inlet communicating with at least twoouter faces of said valve and a fluid outlet through which said flow ofgases pass in use, and

control means for restricting said flow of fluid between said fluidinlet and said fluid outlet located within said body portion,

wherein said body portion and said inlet is adapted such that in usewhen a number of said valves are ganged together their respective saidfluid inlets interconnect to form a common fluid inlet.

In a third aspect, the present invention consists in a valve forcontrolling a flow of fluid comprising a body portion including:

a fluid inlet and a fluid outlet through which said flow of fluid passin use, and

control means for restricting said flow of fluid between said fluidinlet and said fluid outlet located within said body portion andadjustable rotatable therein,

wherein said control means, at least in a substantial portion, iscomprised of a plastics composition.

In a fourth aspect the present invention consists in a valve forcontrolling a flow of fluid comprising a body portion including:

a fluid inlet and a fluid outlet through which said flow of fluid passin use, and

control means for providing a variable restriction on said flow of fluidbetween said fluid inlet and said fluid outlet located within said bodyportion between a low flow setting and a high flow setting and forpreventing said flow of fluid in an offsetting,

wherein said control means is able to switch directly between said highflow setting to said offsetting and vice versa, and further is able toswitch directly from said low flow sewing to said off setting but isprevented from watching directly from said off setting to said low ratesetting.

To those skilled in the art to which the invention relates, may changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of volumetric flow rate versus angular displacementaccording to a prior art device,

FIG. 2 is an exploded view of the present invention in perspective,

FIG. 3 is a cross-section of the present invention,

FIG. 4 is a cross-section of the present invention orthogonal to FIG. 3,

FIG. 5 is a perspective view of the valve member according to thepresent invention,

FIG. 6 is an alternative perspective view of the valve member accordingto the present invention,

FIG. 7 is a cross-section of the valve member according to the presentinvention,

FIG. 8 is an alternative cross section of the valve member orthogonal toFIG. 7,

FIG. 9 is a perspective view of the top plate according to the presentinvention,

FIG. 10 is a perspective view of the shaft according to the presentinvention,

FIG. 11 is an exploded view according to an alternative embodiment ofthe present invention in perspective,

FIG. 12 is a cross-section of an alternative embodiment of the presentinvention,

FIG. 13 is a cross-section of an alternative embodiment of the presentinvention orthogonal to FIG. 12,

FIG. 14 is a perspective view of the body portion from below accordingto an alternative embodiment of the present invention,

FIG. 15 is a perspective view of the shaft according to an alternativeembodiment of the present invention,

FIG. 16 is a graph of the measured volumetric flow rate versus angularposition of the valve member using a prototype of the present invention,

FIG. 17 is a cross-section of the present invention according to thethird preferred embodiment,

FIG. 18 is a cross-section orthogonal to that of FIG. 17,

FIG. 19 is a perspective view of the present invention according to thethird preferred embodiment,

FIG. 20 is an alternative cross-section of the present invention alsoorthogonal to FIG. 17,

FIG. 21 is a perspective view of the valve member according to the thirdpreferred embodiment of the present invention,

FIG. 22 is an alternative perspective view of the valve member accordingto the third preferred embodiment of the present invention,

FIG. 23 is a perspective view of the low setting plug according to thethird preferred embodiment of the present invention,

FIG. 24 is a plan view of a multi-ring burner,

FIG. 25 is a graph showing the flow rate versus control anglecharacteristic according to the third preferred embodiment of thepresent invention,

FIG. 26 is a perspective view of the valve member according to a fourthpreferred embodiment of the present invention, and

FIG. 27 is a perspective view of the ratchet attachment according to thefourth preferred embodiment of the present invention.

DETAILED DESCRIPTION

The present invention attempts to provide a valve which allows moregradual control over the change in gas flow rate in response to therotational adjustment over that of traditional valves. This will beuseful in applications such as gas cook tops where a high level ofcontrol is desired, especially at low flow rates. It will be appreciatedhowever that such a valve will be applicable for control of fluid flowgenerally and is not restricted to gaseous fuels.

A tapered groove on an annular path in the valve member interacts withan inlet port in the valve housing so that as the cross section of thegroove varies according to the angular position of the valve member andaccording to one embodiment of the present invention a linearrelationship exists between changes in angular position and changes inthe volumetric flow rate of the gas. Also inherent in such a valve isthe need to be generically applicable to different types of gas anddifferent sized gas burners especially in the application of gas cooktops. As such the present invention also provides a simple and easymethod of appropriately adjusting the flow rate of the gases at thelower setting such that it is easily adapted to a different type of gasor a different sized burner.

General Construction of the Valve

Now referring to FIG. 2, the gas valve 100 according to the presentinvention, is shown in exploded view. The body portion 102 is shown witha gases inlet 104 extending throughout the body portion 102 to theopposite side and a gases outlet 106 adapted to connect with standardgas fittings. The body portion 102 is constructed from cast aluminiumbut it will be appreciated that many other materials will be equallyapplicable. A valve member 108 is designed to interface with the cavity10 in the interior of the body portion 102, The cavity 110 has a numberof ports 112 which match up with various ports and/or grooves in thevalve member 108. A shaft 19 is provided to allow external control overthe valve member and this slots into a mating cavity 116 atop the valvemember 108. To ensure mechanical integrity of the mechanism and toenclose the gas chamber, a top plate 118 is secured to the top surface120 of the body portion 102. It will be appreciated that the presentinvention could equally be constructed with the body portion 102 splitinto two sections about the bottom face 120 of the chamber 110, with thetop plate 118 integral with the top section. This would then allowaccess to the bottom face 120 of the chamber 110 for machining toimprove the gas sealing properties with the bottom face 132 of the valvemember 108.

Construction of the Valve Member

The valve member shown in more detail in FIGS. 5 to 8 is of a generallycylindrical shape. An annular groove 122 is provided on the periphery toaccommodate an annular rubber “O-ring” seal 123 The top side 124includes a raised cylindrical wall which surrounds the cavity 116 whichcontinues into the interior of the 108. The cylindrical wall 126 isprovided with two slots 128 which provide a means for engaging with theshaft 119. The cavity 116 continues through Be interior of the valvemember 108 to a protrusion 130 on the bottom face 132.

Also included on the bottom face 132 is a tapered groove which followsan annular path and is terminated with a gases port 136 whichcommunicates with the interior of the valve member 108. Both the gasesport 136 and the internal cavity 116 communicate with an outlet passage138 which continues to the exterior of the valve member 108 on its sideface 140. The protrusion 130 on the bottom face 132 also includes a muchsmaller gases port 142 which is provided for gas flow when the valve isset on its “low setting”.

In order to adjust the gas flow at the low setting a rotatable plug 144is screwed into the cavity 116 in the valve member 108 and effectivelyby its angular position determines the effective restriction between thesmall gases port 142 and the main outlet gas passage 138. The shaft 119has a hollow interior such that a screw driver or other such means canengage with a slot 148 provided on the top surface of the rotatable plug144 to adjust the flow rate at the “low setting”.

It will be appreciated by one skilled in the art that an annular taperedgroove provides a number of advantages over prior art systems. Itprovides particular flexibility in providing a desired controlcharacteristic as well as simple efficient manufacture. Further as thevalve member wears over time, the present invention is less likely tosuffer from any deterioration in performance. As the valve member wearsdown over time, it will still seal adequately and to a large extent thegroove will always match up with the cavity inlet port thereforeensuring correct operation.

Operation of the Valve

Referring now to FIGS. 3 and 4, it is seen how in use the variousmembers cooperate. The valve member 108 is forced down upon the bottomface 120 of the chamber 110 in the body portion 102 by a spring 150which provides an opposing force between the shaft 119 (and thereforethe top plate 118) and the valve member 108. This pressure is such thata gas tight seal exists between the bottom surface 132 of the valvemember 108 and the bottom face 120 of the chamber 110. The gases flowfrom the inlet port 104, to the cavity 110, via a cavity inlet port 146.As the valve member 108 rotates the cavity inlet port 146 is varied incross section due to the variation in width of the tapered groove at thepoint of intersection. The gas then flows through the remainder of thetapered groove to the gases port 136 at its end through the body of thevalve member through to an outlet port 138 wherein it flows around thecircumference of the chamber 110 until it meets up with the main gasoutlet port 106. The gas is prevented from flowing up any further intothe chamber 110 by the “O ring” seal 123.

In the “off setting” the valve member 108 is rotated such that the inletport 152 does not meet up with the tapered groove at all and is closedoff by the flat bottom face 132 of the valve member 108. In the lowsetting the small gases port 142 in the protrusion 130 on the bottomface 132 of the valve member 108 matches up with a smaller gases inletport 152 connected to the inlet 104. Meanwhile the main gas inlet portis blocked off and gas is prevented from flowing down the taperedgroove. Therefore the only restriction on the gas flow at the lowsetting is determined by the angular position of the rotatable plug 144.In any other setting other than low or off the gas flow is determined byangular position of the valve member.

Shaft and Body Configuration

Referring now to FIG. 9 and FIG. 10, we can see how the shaft 119 andthe top plate 118 interact in the various different settings. In FIG. 9we see the underside of the top plate 118 which has a circular hole 155in the centre of the plate with three notches 154, 156, 158 on the edgein close proximity. The notches interact with the larger cam 162 on thebase of the exterior of the shaft 119. Due to the action of the spring150 the shaft 119 must be depressed and rotated in order to move thevalve from the out of the “off” notch 156. In the “low setting” thelarge cam 162 is positioned in the low setting notch 154 and again hasto be pushed and rotated to be moved to any other position. Once out ofthe low setting notch 154 the shaft may be rotated freely from anyposition between there and the high setting notch 158. It will beappreciated that when the shaft 119 is freely rotated and the large cam162 then meets one of the grooves then it will snap into place and willstay locked in that position until the shaft is depressed and thenrotated. Again as already described the shaft 119 has a hollow bodyallowing access to the rotatable plug 144 for adjustment of the gas flowat low setting.

To provide a rigid and smooth rotation at the shaft 119, a secondsmaller cam 166 is located at the bottom of the shaft, diametricallyopposite the larger cam 162.

Second Preferred Embodiment

Referring now to FIGS. 11-15 showing a second embodiment of the presentinvention in which the shaft extends down into an inlet chamber andincludes a circular disc which as well as providing the locking actionon the off, low and high settings also plays some part in the actualvalve action of the mechanism.

The body portion 200 includes a lower chamber 202 and an upper chamber204. The upper chamber houses a valve member 206 substantially asdescribed in the first embodiment. Instead of a spring the compressiveforce between the lower face of the valve member 206 and the bottom face208 of the upper chamber 204 is provided by a rubber O ring seal 210which provides a reactive force between the upper plate 212 and theupper surface 214 of the valve member 206.

The lower chamber 202 forms part of an inlet manifold, with inlet ports201 on two opposing side walls at the body portion 200. The outlet port203 is located on a third side wall at the body portion 200 and, as forthe first embodiment is adapted for connection with standard gasfittings.

The operation of the valve is substantially similar to that describedpreviously in the first embodiment The gas flows from the inlet ports201 into the lower chamber 202 and through the upper chamber inlet port232 As with the first embodiment, the rotation of the valve member 206varies the flow of gases, because of the varied cross-section of thetapered annular groove on its base as it intersects with the upperchamber inlet port 232. The gases then flow through the groove up apassage in the valve member 206, into the upper chamber 204 and outthrough the outlet 203.

The shaft 216 includes a solid circular disc 218 attached at its bottomend. The shaft itself in use cooperates with an axial hole 220 extendingthe length of the valve member 206. The shaft is permitted to movevertically (to a point) independently of the valve member but movescooperatively with the valve member in response to any rotationalmovement The shaft includes a flat section 229 which extends partiallyalong the length of the shaft 216 for attaching a control knob. As wasdescribed in the first embodiment in the off, low and high setting theshaft is locked in place and needs to be depressed before it can berotated. The locking mechanism consists of notches 239 for each setting,in the divider between the two cavities, and a cam 236 at the base ofthe shaft 216. A spring 222 is provided between the disc 218 at thebottom of the shaft 216 and the bottom plate 224 of the body portion 200to resist depression of the shaft.

In order to adjust the flow at low setting the circlip 226 must beremoved from the shaft 216 so that the alignment of the spline 228 onthe shaft 216 and the mating member 228 and the valve member 206 can beadjusted. Practically this will require the locking nut 230 to beloosened so the valve member 206 can be freely rotated with respect tothe shaft 216. The actual flow rate at the low setting is dependent onthe width of the groove intersecting the upper chamber inlet 232 whenthe cam 236 a the base of the shaft 216 is locked in the low settingnotch. This differs from the first embodiment in that there is noseparate flow path for the low setting. A circlip 226 is attached to theshaft 216 on a slot 238 to ensure that it can only be depressed to acertain extent so as not to over-compress the spring 222.

In a variation of this embodiment the cam 236 and notches can bereplaced by a protrusion 240 on the upper face on the disc 218. In theoff setting the protrusion would fit into die upper chamber inlet port232, sealing it off. In low and high setting it might rest in dimples inthe roof of the lower chamber 202.

Combined Inlet Manifold

As described in the various embodiments, the valve may be constructedwith an inlet manifold which runs from one side of the valve to theother. This then allows a common inlet manifold to be formed when thevalves are gained together side by side. When used in thisconfiguration, the inlet on one side of the ganged valves is blocked offand the other connected to the gas supply. The individually controlledsupply from each valve is then supplied from the respective outlets ofeach valve. This not only saves on equipment to connect to the gassupply, but it saves on space and for example allows a more compact cooktop. The individual valves may be attached side by side or separatedusing spacers, depending on requirements.

The transfer function relating shaft rotation to volumetric flow rateaccording to the preceding embodiment of the present invention is shownin FIG. 16. This illustrates a substantially linear relationship ofvolumetric flow rate against shaft rotation, between the low setting 250and the high setting 252. It will of course be appreciated thatvariations in how the taper varies will allow the relationship to betailored to whatever might suit the particular application. Inparticular a more logarithmic/exponential relationship might be useful,since for cook top applications fine control is usually only required atlow flow rates.

Third Preferred Embodiment

It will be appreciated in the foregoing that there are a number ofconfigurations available to achieve the present invention. In a thirdpreferred embodiment shown in FIGS. 17 to 20, the present invention isillustrated including a conical valve member 300. Apart from the shapeof the valve member 300, the third preferred embodiment is characterisedby the fact that the tapered groove, in this case, is on the side of thevalve member. The third embodiment may provide a simple means ofcontrolling a multiple ring gas burner by providing a number of outletports in various positions around the body portion 304 of the valve.

The valve is generally disposed as depicted in FIG. 19, with a bodyportion 304 including a main chamber 301, a main inlet port 306, and anoutlet port 324.

The gas flows in through the main inlet port 306 which is effectively acylindrical cavity running from one side of the body portion to theother. In the middle of the main inlet port 306 the gas flows throughthe chamber inlet port 308 which interfaces with the rotatable valvemember 300, itself located within the main chamber. The main cavity 301is sealed on top with a face plate and rubber seals (not shown).

As mentioned in the preceding embodiment, grooves might be provided onthe underside of the face plate so that the valve locks into place inthe off, low and high settings. Optionally, farther grooves might beprovided such that the entire control range is divided up into discretesteps if so required.

The rotatable valve member 300, shown in more detail in FIGS. 21 and 22,is of generally conical shape including a hollow centre section 310. Thetapered groove 302 runs radially around the side face 340 of the valvemember 300. At the wide end of the tapered groove 302 is an axialchannel 318 running downwardly, which when located in the main cavity301 puts the tapered groove 302 in fluid communication with the space322 below the valve member 300. At the narrow end of the tapered groove302 (either in the groove or beside it), a low setting port 312 providesa further gas flow path through to the hollow centre 310. Located in thehollow centre section 310 is a rotatable low setting plug 314 shown inmore detail in FIG. 23. Similarly to the valve member 300, the lowsetting plug 314 includes a tapered groove 316 running radially aroundthe side of is in the preferred form, a conical member. The low settingplug 314 also has a downward axial channel 320 at the wide end of itstapered groove 316.

For the valve member 300 (and the low setting plug 314) the gas flowsfrom the inlet port 308 (312) into the tapered groove 302 (316),radially around to the wide end of the tapered groove to a downwardaxial channel 318 (320), which communicates with the lower empty portion322 of the main cavity 301. From here it flows into the main outlet port324 which is connected to the appropriate burner ring.

Provided on the upper surface of the valve member 300 arc slots 327which provide a means to engage a shaft (not shown) which allowsexternal control over the valve member and therefore over the gas flow.Similarly, the low setting plug includes a slot 328 which allows the gasflow at low setting to be adjusted in use through the middle of thehollow shaft. It will be appreciated that the only time that gas willflow through the low setting plug 314 is when the valve member 300 isrotated to the low setting position whereby the low setting port 312matches up with and is in fluid communication with the chamber inletport 308. Alternatively if the low setting port 312 is actually insidethe groove 362 then gas will flow when the valve is in any “on” setting.

In a further improvement shown in more detail in FIGS. 19 and 20, thethird preferred embodiment of the present invention provides a means ofcontrolling multiple ring burners. In order to provide this, the bodyportion 304 includes at least one additional outlet port 326 headditional outlet port 326 is located somewhat adjacent to the memberinlet port 308 such that it also will interface with the tapered groove302 and therefore will only be in fluid communication therewith for alimited angle of control.

A multiple ring burner 330 such as might be controlled by the preferredembodiment of the present invention is shown in FIG. 24. It includes anouter ring 332 supplied by an outer supply port 334 and an inner burnerring 336 which is supplied by an inner ring port 338. FIG. 25illustrates the expected control characteristic of the gas supplied tothe outer burner ring 350 and the inner burner ring 352 according to thethird preferred embodiment. This illustrates that in this form thepresent invention provides the ability to control the gas burner with ahigh level of flexibility and sensitivity, especially at the low ratesof gas flow where high control is necessary.

Plastic Construction

It will be appreciated that in the previous embodiments the valve mightbe constructed from aluminium or brass materials as have beentraditionally used. The preferred embodiment of at least the valvemember is rotatable. At least in one form, the present invention mightbe constructed using a plastics composition which will provide hardwearing properties, easy and inexpensive manufacturing, and results in asmooth adjustment action. One of the preferred compositions envisagedincludes a substantial component of nylon based derivative. It will beappreciated that a number of other plastics compositions will also besuitable to achieve this purpose. When the entire valve constructed fromplastics, ganging a number of valves together to form a common inletmanifold such constructions will improve ease of manufacture and reducemanufacturing and raw material costs.

Ratchet Attachment

Referring now to FIGS. 26 and 27 a fourth preferred embodiment of thepresent invention is shown which allows generally free rotation of thevalve member within the body portion except that a direct movement fromthe off setting to the low flow rate setting is prevented. In thisfashion the present invention allows the valve to be turned off fromboth the high flow rate and the low flow rate setting, improving theease of use, while still retaining the safety feature of prevention ofswitching on the valve straight to the low setting. The top face 400 ofthe valve member 402 includes a small ramped portion 404 with a flatface 406 at one end. Effectively during rotation in the anti clockwisedirection from the low flow rate setting to the off setting and from theoff setting to the high flow rate setting the ramped portion 404 will bein front of the flat face 406. In this fashion the ramped portion 404slides unobstructed underneath the ratchet attachment 408 which isattached over the top of the valve member to the body portion, describedin previous embodiments.

The ratchet attachment 408 includes a ratchet leg 410 juxtapositionedwithin the path of travel of the ramp portion 404 and the flat face 406.Only when the valve member 402 is rotated clockwise and where the flatface 406 meets up with the distal end 412 of the ratchet leg 410 isfurther rotation prevented.

Further the ratchet attachment 408 includes a number of apertures 414 inits mid section 416. These apertures 414 are provided, as described inthe preceding embodiments to allow the gas valve to lock into the offhigh and low flow settings, preventing them from being dislodgedunintentionally.

Further, a number of indentations 418 are provided in an annular pathfollowing that of the apertures, to allow stepped rotation of the valvemember. The indentations 418 (as well as the apertures), engage with aridge associated with the control member (not shown). In this fashionthe ridge locks into place on high, low and off settings and partiallylocks into place at the intermediate settings between the high and lowsetting. This stepped rotation may be desirable in some applicationswhere the user wants to consistently set the airflow rate at aparticular setting.

Thus an improved gas valve has been described with a more gradual andcontrollable variation of the flow rate. It offers flexibility in thatthe low setting flow rate can be easily adjusted in situ to adapt todifferent fuels and burners. The valve itself is simple and modular andmay be ganged together in series with a number of valves It provides theflexible control over multiple ring burners and in a further improvementmay be constructed from plastic. Also to improve ease of use the valvemay be turned off in any direction of rotation, but only be turned on tothe high setting.

What is claimed is:
 1. A valve for controlling a flow of fluidcomprising: a body portion including a fluid inlet and a fluid outletthrough which said flow of fluid pass in use, and frusto conical controlmeans for restricting said flow of fluid between said fluid inlet andsaid fluid outlet located within said body portion and adjustablyrotatable therein, wherein one of said body portion or the conicalsurface of said control means includes a tapering groove on an annularpath and the other includes a control port, in use said control portintersecting with said annular groove such that the position of saidintersection varies according to the angular position of said controlmeans, such that in use there is a gradual variation in the flow rate ofsaid flow of fluid with respect to variations in the angular position ofsaid control means over a substantial angle of rotation of said controlmeans, said intersection being within a flow path between said fluidinlet and said fluid outlet.
 2. A valve for controlling a flow of fluidas claimed in claim 1 wherein said flow of fluid is a flow of gaseousfuels.
 3. A valve for controlling a flow of fluid as claimed in claims 1or 2 wherein the flow rate of said flow of fluid is controllable betweena low flow rate setting and a high flow rate setting, wherein in usesaid control means substantially locks in place when adjusted to saidlower setting or said high setting, whereby requiring additional appliedforce to be adjusted therefrom, with respect to that at any other flowrate of said flow of fluid.
 4. A valve for controlling a flow of fluidas claimed in any one of claims 1 to 3 wherein the relationship betweensaid gradual variation of the flow rate with respect to said angularposition of said control means is substantially linear and said flowrate relates to the volumetric flow rate of said flow of fluid for aconstant pressure.
 5. A valve for controlling a flow of fluid as claimedin claim 3 further comprising actuation means including a firstadjustment means and a second adjustment means operatively connectedwith said control means, said first adjustment means allowing externaladjustment of said angular position of said control means, in use theflow rate of said flow of fluid at said low setting depending therelative position of said second adjustment means to said firstadjustment means, said second adjustment means thereby allowing externaladjustment of the flow rate of said fluid flow at said low setting.
 6. Avalve for controlling a flow of fluid as claimed in claim 5 wherein saidcontrol means further comprises at least two fluid flow paths, wherein afirst fluid flow path primarily conveys said flow of fluid, but isbypassed on said low setting whereby said flow of fluid is conveyed by asecond fluid flow path, and said relative position of said secondadjustment means with respect to said first adjustment means adjustablyrestricting the flow rate of said flow of fluid at said low setting. 7.A valve for controlling a flow of fluid as claimed in claim 5 whereinsaid actuation means includes an extension portion, said extensionportion being within a flow path between said fluid inlet and said fluidoutlet and wherein in use said control means is adjusted to an offsetting, said flow of fluid is blocked by said extension portion.
 8. Avalve for controlling a flow of fluid as claimed in any one of claims 1to 7 wherein when said control means is adjusted to said off positionsaid control port and said tapering groove do not intersect.
 9. A valvefor controlling a flow of fluid as claimed in any one of claims 1 to 8wherein said annular groove is semicircular in cross-section.
 10. Avalve for controlling a flow of fluid as claimed in any one of claims 1to 8 wherein said annular groove is triangular in cross-section.
 11. Avalve for controlling a flow of fluid comprising: a body portionincluding a fluid inlet and a fluid outlet through which said flow offluid pass in use, and control means for restricting said flow of fluidbetween said fluid inlet and said fluid outlet located within said bodyportion and adjustably rotatable therein, wherein one of said bodyportion or said control means includes a tapering groove on an annularpath and the other includes at least two control ports being physicallyseparated, in use each of said control ports intersecting with saidannular groove such that the position of said intersections variesaccording to the angular position of said control means, such that inuse there is a gradual variation in the flow rate of said flow of fluidthrough each of said control ports with respect to variations in theangular position of said control means over a substantial angle ofrotation of said control means, said intersections being within a flowpath between said fluid inlet and said fluid outlet, and for a givenangular position of said control means the flow rate through a first ofsaid control ports will differ from that through a second of saidcontrol ports, said first control port being in fluid communication witha first fluid:, outlet and said second control port being in fluidcommunication with a second fluid outlet.
 12. A valve for controlling aflow of fluid as claimed in claim 11 wherein said first control port andsaid second control port being on said angular path, and being separatedby a predetermined angular distance.
 13. A valve for controlling a flowof fluid as claimed in claim 11 wherein there being a second taperinggroove, said first control port being in the angular path of and therebyintersecting with said first annular groove and said second control portbeing in the annular path of and thereby intersecting with said secondannular groove.
 14. A valve for controlling a flow of fluid comprising:a body portion including a fluid inlet and a fluid outlet through whichsaid flow of fluid pass in use, and control means for restricting saidflow of fluid between said fluid inlet and said fluid outlet locatedwithin said body portion and adjustably rotatable therein, wherein oneof said body portion or said control means includes a tapering groove onan annular path and the other includes a control port, in use saidcontrol port intersecting with said annular groove such that theposition of said intersection varies according to the angular positionof said control means, such that in use there is a gradual variation inthe flow rate of said flow of fluid with respect to variations in theangular position of said control means over a substantial angle ofrotation of said control means, said intersection being within a flowpath between said fluid inlet and said fluid outlet, the flow rate ofsaid flow of fluid being controllable between a low flow rate settingand a high flow rate setting, and said control means able to be adjustedinto a definite number of intermediate settings between said low settingand said high setting, said control means being partially locked inplace in each said intermediate setting whereby a significant force mustbe applied to said control means to dislodge it from one setting toanother.
 15. A valve for controlling a flow of fluid as claimed in claim14 further comprising actuation means operatively connected to saidcontrol means, thereby allowing external adjustment of said angularposition of said control means, said actuation means engaging with saidbody portion, said engagement being such that said control means may bepartially locked in place in said intermediate settings.
 16. A valve forcontrolling a flow of fluid as claimed in claim 15 wherein saidengagement comprises a ridge or petruburance on said actuation meansengaging with in plurality of indentations or notches in said bodyportion, whereby shifting said ridge from one said notch to anotherrequires a significant rotational force to be applied to said actuationmeans.
 17. A valve for controlling a flow of fluid as claimed in any oneof claims 1 to 16 wherein said inlet including a fluid inlet manifoldhaving ports on at least two outer faces of said valve, wherein saidbody portion and said inlet manifold are adapted such that in use when anumber of said valves are ganged together their respective portsinterconnect to form a common fluid inlet, in use terminated at one endand supplied with fluid at the other.
 18. A valve for controlling a flowof fluid comprising a body portion including: a fluid inlet and a fluidoutlet through which said flow of fluid pass in use, and control meansfor providing a variable restriction on said flow of fluid between saidfluid inlet and said fluid outlet located within said body portionbetween a low flow setting and a high flow setting and for preventingsaid flow of fluid in an off setting, wherein said control means isprevented from switching directly from said off setting to said low flowsetting, or any setting other than said high flow setting.
 19. A valvefor controlling a flow of fluid as claimed in claim 18 wherein saidcontrol means further comprises a protrusion on one face thereof, saidprotrusion having and angled face portion and a flat face potion, andsaid body portion further comprising a ratchet means whereby thecooperation of said ratchet means and said protrusion allowing rotationgenerally in one direction coinciding with the switching from said lowrate setting to said off setting and from said off setting to said highflow setting, and to partially allow rotation in the opposite directioncoinciding with switching from said high flow setting to said offsetting but preventing further rotation where said ratchet means engageswith said flat face to thereby prevent switching directly from said offsetting to said low flow setting.